Shareholders are accustomed to raking in cash from Viacom’s prodigious stock repurchases and dividends. So this morning’s news that it will spend £450M ($757M) to buy the UK broadcaster has many wondering whether the party’s over. But execs told analysts in a conference call not to worry: “It will not impact the buy back program at all,” COO Tom Dooley says. The funds to buy Channel 5 were already parked overseas (that means no U.S. taxes) so “it’s not cash that would have been available for the stock buyback program” in the U.S. What’s more, the investment “will yield a very high return” — he says low to mid teen percentages, comparable to other company operations — and includes £125M of net losses that can be used to lower Viacom’s taxes. CEO Philippe Dauman added that the deal will boost operating income in the first year after it closes and will enable Viacom to increase spending for programming that can be used on “existing and future networks around the world.”

We’ll see whether investors are persuaded. Viacom shares are down slightly in early trading, despite this AM’s disclosure of stronger than expected earnings for the first three months of this year. Bernstein Research’s Todd Juenger, a frequent Viacom critic, says that “if Viacom’s content would drive better results for the network, then Channel 5 should have been acquiring Viacom content already. It was certainly available for sale.”

While analysts were most interested in Channel 5, Dauman noted that Comedy Central will send Stephen Colbert off “in style” next year when he leaves to replace David Letterman at CBS’ The Late Show — and will “reinvent the 11:30 slot.”